Re: [pdf-devel] New DCT decode filter patch

[jemarch]

Hi Yang.

   This patch should be OK for DCT decode filter....

As you can see in the 7.4.8 section of the ISO PDF specification the
DCT decoder uses one parameter:

      ColorTransform (integer, optional)

        A code specifying the transformation that shall be performed
        on the sample values:

        0 - no transformation
        1 - If the image has three colour components, RGB values shall
        be transformed to YUV before encoding and from YUV to RGB
        after decoding. If the image has four components, CMYK values
        shall be transformed to YUVK before encoding and from YUVK to
        CMYK after decoding. This option shall be ignored if the image
        has one or two colour components.
  
        If the encoding algorithm has inserted the Adobe-defined
        marker code in the encoded data indicating the ColorTransform
        value, then the colours shall be transformed, or not, after
        the DCT decoding has been performed according to the value
        provided in the encoded data and the value of this dictionary
        entry shall be ignored. If the Adobe-defined marker code in
        the encoded data indicating the ColorTransform value is not
        present then the value specified in this dictionary entry will
        be used. If the Adobe-defined marker code in the encoded data
        indicating the ColorTransform value is not present and this
        dictionary entry is not present in the filter dictionary then
        the default values of ColorTranform shall be 1 if the image
        has three components and 0 otherwise.

Your implementation does not seem to be aware of the parameter.